Time-course pattern of carrot storage root growth in a solid substrate, sub-irrigation culture system

A fast-maturing carrot cultivar that produces small storage roots termed "mini carrot" was grown in a solid substrate, sub-irrigation culture system placed in a phytotron glass room with a controlled air temperatiffe of 23°C and relative humidity of 700o. Patterns of storage root growth and accumulation of chemical compounds in the roots were investigated. Optimal time for harvest determined by the root size was limited to 1 week between 9 and 10 weeks after seeding. Fresh weight of the storage root increased by the greatest amount between 8 and 9 weeks after seeding. However, increase in length, diameter, and fresh weight of the storage roots reached a plateau at 11 weeks after seeding. The increase in β-carotene and sucrose content was slow until 9 weeks after seeding just before the optimal harvest time. Thereafter, accumulation of these nutrients became more active, and their contents increased by approximately 2-fold at 3 weeks after the optimal harvest time.